Plasma processing apparatus

ABSTRACT

A plasma processing apparatus includes a reaction chamber for processing a workpiece with plasma which is generated by using one or more gases, a gas supplying means which pulsatively supplies the gases to the reaction chamber, and an exhaust means for exhausting the reaction chamber, wherein a gas supplying direction by said gas supplying means is arranged to correspond with an exhausting direction by said exhausting means.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a plasma processing apparatusfor deposition of a thin film onto a surface of a workpiece or foretching a surface of a workpiece.

[0003] 2. Description of the Related Art

[0004] Conventionally, as an apparatus for processing a workpiece, forexample, a substrate or a semiconductor wafer (hereinafter, alsoreferred to as a “wafer”) using plasma in a processing chamber, aparallel plate type plasma processing apparatus using radio frequency(RF) plasma has been widely utilized. Such type of plasma processingapparatus has a constitution that plasma is generated between itsparallel plate electrodes by applying radio frequency voltage to one orboth of the electrodes, thereby allowing ions become incident on thesurface of the workpiece to be processed by an RF self-bias voltagebetween the plasma and the workpiece; and then a processing, forexample, etching processing are performed.

[0005] However, according to the above mentioned parallel plate typeplasma processing apparatus, it was not easy to achieve fine-patternprocessing and low-damage which were required for the production ofsemiconductor devices as the integrated density thereof has beenincreased and the performance thereof has been enhanced. That is, inorder to achieve such a process, it is important to generate and controla low-pressure, high-density plasma. Such plasma is required to have auniform density over a large area so that it may process a wafer havinga large diameter.

[0006] To solve the above requirements, various kinds of plasma sourcesand processing methods have been proposed and applied to thesemiconductors processing. Among those, a plasma processing apparatusshown in FIG. 14, which uses a pulse gas valve for pulsatively supplyingone or more processing gases to a reaction container and is disclosed inJapanese Patent Kokai Publication No. 263353/1995, has been favorablyprospected for application to semiconductor processing field. It isbecause such a plasma processing apparatus enables to decrease theplasma temperature by utilizing a pressure difference between the plasmagenerating chamber and the processing chamber. In FIG. 14, referencenumeral 2 designates a processing chamber wherein a workpiece, forexample a wafer 8 is processed with plasma, reference numeral 3designates a plasma generating chamber wherein plasma is generated, andreaction chamber I consists of these two chambers 2 and 3. Referencenumeral 4 designates a partition plate for partitioning the processingchamber 2 from the plasma generating chamber 3, reference numeral 5designates holes which are provided in the partition plate 4 and makesthe processing chamber 2 in connection with the plasma generatingchamber 3, reference numeral 6 designates a exhaust port, referencenumeral 7 designates a stage, and reference numeral 9 designates a pulsegas valve which pulsatively supplies one or more gases to the plasmagenerating chamber 3. Reference numeral 10 designates a drive means forthe pulse gas valve 9, reference numeral 11 designates a gas introducingline, reference numeral 12 designates a wave guide, reference numeral1.3 designates a window for introducing microwave, and reference numeral14 designates a magnetic field coil.

[0007] In this plasma processing apparatus, the plasma generated in theplasma generating chamber 3 is supplied to the processing chamber 2through holes 5 in the partition plate 4. In this case, the plasma isintroduced into the processing chamber 2 as a supersonic free jet by thepressure difference between the plasma generating chamber 3 and theprocessing chamber 2, and simultaneously the temperature of the plasmadecreased, so that an etching processing with anisotropic profile andlow-damage may be performed. Further, it is possible to processuniformly the wafer having a large diameter by selecting the sizes andthe arrangement of the holes 5.

[0008] According to the above-mentioned plasma processing apparatususing pulse gas valve, the processing gases instantaneously diffusesthroughout the reaction chamber 1 as a supersonic free jet due to apressure difference caused by closing and opening operation of the pulsegas valve 9, and then become incident on the surface of wafer 8.Therefore, it was contemplated that a uniformalization of the processingrate of wafer 8 and the processed profile over the wafer 8 were achievedwithout deviation of gas flow and pressure in the reaction chamber 1.

[0009] However, according to the present inventors' further detailedexamination as to the gas flow, it was found that there is a possibilityto cause a problem that uniform processing rate and processed profileover the wafer 8 are not always achieved. Such a problem may be causedby a deviation of flow of the processing gases and reaction product, forexample, in the case just before the pulse gas valve 9 is opened, in thecase when a repeating period of closing and opening of the pulse gasvalve 9 is short, and in the case when the pressure difference is toosmall to sufficiently produce a supersonic free jet, for example when aclosing time of the pulse gas valve 9 is too short. In other word, undera condition where a supersonic free jet is satisfied, processing ofwafer 8 is independent of the arranging positions of the pulse gas valve9 and exhaust port 6. However, under the condition where a supersonicfree jet is not satisfied, the gas flow and pressure in the reactionchamber 1 may be deviated depending on the arranging positions of thepulse gas valve 9 and exhaust port 6, which may become a problem toaffect the processability of wafer 8.

SUMMARY OF THE INVENTION

[0010] In order to solve the above-mentioned problems of the prior art,it is an object of the present invention to achieve uniformalization ofthe processing rate and the processed profile over the wafer under acondition even when a supersonic free jet is not formed in the plasmaprocessing apparatus, which is provided with a means for pulsativelysupplying one or more gases into the reaction chamber.

[0011] In a first aspect of the present invention, the plasma processingapparatus comprises a reaction chamber for processing a workpiece withplasma which is generated by using one or more gases, a gas supplyingmeans which pulsatively supplies the gases to the reaction chamber, andan exhaust means for exhausting the reaction chamber, wherein a gassupplying direction by said gas supplying means is arranged tocorrespond with an exhausting direction by said exhausting means.

[0012] In a second aspect of the present invention, the plasmaprocessing apparatus has, in addition to the constitution according tothe first aspect of the present invention above mentioned, aconstitution that, when observed from a direction perpendicular to aface to be processed of the workpiece, the gas supplying direction bysaid gas supplying means directs to a center of the reaction chamber,and the exhausting means are arranged in the reaction chamber so that anassumed straight line extending from the center of the reaction chamberto the exhausting means is oriented at an angle from −45 degree to +45degree relative to a line from the gas supplying means to the center ofthe reaction chamber and the exhausting direction by the exhaustingmeans from the center of the reaction chamber is also oriented at thesame angle as above.

[0013] In a third aspect of the present invention, the plasma processingapparatus comprises a reaction chamber for processing a workpiece withplasma which is generated by using one or more gases, a gas supplyingmeans which pulsatively supplies the gases to the reaction chamber, andan exhaust means for exhausting the reaction chamber, wherein the shapeof the reaction chamber is axially symmetrical with respect to ancentral axis of the reaction chamber, the gas supplying means arearranged on the central axis or at axially symmetrical positions withrespect to the central axis of the reaction chamber, and the exhaustmeans are also arranged at axially symmetrical positions with respect tothe central axis of the reaction chamber.

[0014] In a fourth aspect of the present invention, the plasmaprocessing apparatus comprises a reaction chamber for processing aworkpiece with plasma which is generated by using one or more gases, agas supplying means which pulsatively supplies the gases to the reactionchamber, and an exhaust means for exhausting the reaction chamber,wherein the amount of the gases supplied by the gas supplying means isset relatively small in the proximity of the exhaust means and theamount of the gases supplied by the gas supplying means is increased ata position where its distance from the exhaust means increases.

[0015] In a fifth aspect of the present invention, the plasma processingapparatus has, in addition to the constitution according to the fourthaspect of the present invention above mentioned, a constitution that anumber of the gas supplying means is set relatively small in theproximity of the exhaust means and the number of the gas supplying meansis increased at a position where its distance from the exhaust meansincreases.

[0016] In a sixth aspect of the present invention, the plasma processingapparatus has, in addition to the constitution according to the fourthaspect of the present invention above mentioned, a constitution that thegas flow rate is set at a relatively small value in the proximity of theexhaust means and the value of the gas flow rate is increased at aposition where its distance from the exhaust means increases.

[0017] In a seventh aspect of the present invention, the plasmaprocessing apparatus comprises a reaction chamber for processing aworkpiece with plasma which is generated by using one or more gases, agas supplying means which pulsatively supplies the gases to the reactionchamber, an exhaust means for exhausting the reaction chamber, apartition plate which partitions the plasma generating chamber whereinplasma is generated from the processing chamber wherein the workpiece isprocessed with the plasma, and holes which are provided in the partitionplate and make the processing chamber in connection with the plasmagenerating chamber, wherein at least one of the number and the size ofthe holes is changed depending on the distance thereof from theexhausting means, thereby an opening ratio of the holes being set at arelatively small figure in the proximity of the exhaust port and thefigure thereof being relatively increased at a position where itsdistance from the exhaust means relatively increases.

[0018] In a eighth aspect of the present invention, the plasmaprocessing apparatus has, in addition to the constitution according tothe seventh aspect of the present invention above mentioned, aconstitution that a number of the holes is set at a relatively smallfigure in the proximity of the exhaust port and the number of the holesis relatively increased at a position where its distance from theexhaust means relatively increases.

[0019] In a ninth aspect of the present invention, the plasma processingapparatus has, in addition to the constitution according to the seventhaspect of the present invention above mentioned, a constitution that asize of the hole is set at a relatively small figure in the proximity ofthe exhaust port and the size of the hole is relatively increased at aposition where its distance from the exhaust means relatively increases.

[0020] According to the first aspect of the present invention, since ithas a constitution that the plasma processing apparatus comprises areaction chamber for processing a workpiece with plasma which isgenerated by using one or more gases, a gas supplying means whichpulsatively supplies the gases to the reaction chamber, and an exhaustmeans for exhausting the reaction chamber, wherein a gas supplyingdirection by said gas supplying means is arranged to correspond with anexhausting direction by said exhausting means, even if a supersonic freejet is not formed, the gas flow and the pressure from the gas supplyingmeans to the exhaust ports may be unified, so that a uniform processingover the workpiece can be achieved.

[0021] According to the second aspect of the present invention, since,in addition to the constitution according to the first aspect of thepresent invention above mentioned, it has a constitution that, whenobserved from a direction perpendicular to a face to be processed of theworkpiece, the gas supplying direction by said gas supplying meansdirects to a center of the reaction chamber, and the exhausting meansare arranged in the reaction chamber 1 so that a line extending from thecenter of the reaction chamber 1 to the exhausting means is oriented atan angle from −45 degree to +45 degree relative to a line from the gassupplying means to the center of the reaction chamber 1 and theexhausting direction by the exhausting means from the center of thereaction chamber 1 is also oriented at the same angle as above, even ifthe mounting positions of the gas supplying means and the exhaustingmeans are limited in the apparatus due to a requirement of theconstitution of the apparatus, a uniform processing over the workpiecemay be achieved as long as the arrangement of the exhausting means andthe exhausting direction are set within the angle above mentioned.

[0022] According to the third aspect of the present invention, since ithas a constitution that the plasma processing apparatus comprises areaction chamber for processing a workpiece with plasma which isgenerated by using one or more gases, a gas supplying means whichpulsatively supplies the gases to the reaction chamber, and an exhaustmeans for exhausting the reaction chamber, wherein the shape of thereaction chamber is axially symmetrical with respect to an central axisof the reaction chamber, the gas supplying means are arranged on thecentral axis or at axially symmetrical positions with respect to thecentral axis of the reaction chamber, and the exhaust means are alsoarranged at axially symmetrical positions with respect to the centralaxis of the reaction chamber, even if a supersonic free jet is notformed, the gas flow and the pressure from the gas supplying means tothe exhaust ports may be unified, so that a uniform processing over theworkpiece can be achieved.

[0023] According to the fourth aspect of the present invention, since ithas a constitution that the plasma processing apparatus comprises areaction chamber for processing a workpiece with plasma which isgenerated by using one or more gases, a gas supplying means whichpulsatively supplies the gases to the reaction chamber, and an exhaustmeans for exhausting the reaction chamber, wherein the amount of thegases supplied by the gas supplying means is set relatively small in theproximity of the exhaust means and the amount of the gases supplied bythe gas supplying means is increased at a position where its distancefrom the exhaust means increases, even if a supersonic free jet is notformed, the deviation or unevenness of pressure and gas flow within thereaction chamber can be prevented, so that a uniform processing over theworkpiece can be achieved.

[0024] According to the fifth aspect of the present invention, since, inaddition to the constitution according to the fourth aspect of thepresent invention above mentioned, it has a constitution that a numberof the gas supplying means is set relatively small in the proximity ofthe exhaust means and the number of the gas supplying means is increasedat a position where its distance from the exhaust means increases, theconstitution according to the fourth aspect can be achieved with asimple constitution and a uniform processing over the workpiece can beachieved.

[0025] According to the sixth aspect of the present invention, since, inaddition to the constitution according to the fourth aspect of thepresent invention above mentioned, it has a constitution that the gasflow rate is set at a relatively small figure in the proximity of theexhaust means and the figure of the gas flow rate is increased at aposition where its distance from the exhaust means increases, even if aplurality of gas supplying means are used and each of them are arrangedwithin the reaction chamber at optional position respectively, theconstitution according to the fourth aspect can be achieved and auniform processing over the workpiece can be achieved.

[0026] According to the seventh aspect of the present invention, sinceit has a constitution that the plasma processing apparatus comprises areaction chamber for processing a workpiece with plasma which isgenerated by using one or more gases, a gas supplying means whichpulsatively supplies the gases to the reaction chamber, an exhaust meansfor exhausting the reaction chamber, a partition plate which partitionsthe plasma generating chamber wherein plasma is generated from theprocessing chamber wherein a workpiece is processed with the plasma, andholes which are provided in the partition plate and make the processingchamber in connection with the plasma generating chamber, wherein atleast one of the number and the size of the holes is changed dependingon the distance thereof from the exhausting means, thereby an openingratio of the holes being set at a relatively small figure in theproximity of the exhaust port and the figure thereof being relativelyincreased at a position where its distance from the exhaust meansrelatively increases, even if a supersonic free jet is not formed, auniform rate or transport speeds of the plasma and the gases from theplasma generating chamber to the processing chamber can be achieved, sothat deviation or unevenness of pressure and gas flow within thereaction chamber 1 may be prevented. Accordingly, a uniform processingover the workpiece may be achieved.

[0027] According to the eighth aspect of the present invention, since,in addition to the constitution according to the seventh aspect of thepresent invention above mentioned, it has a constitution that a numberof the holes is set at a relatively small figure in the proximity of theexhaust port and the number of the holes is relatively increased at aposition where its distance from the exhaust means relatively increases,the constitution according to the seventh aspect can be achieved with asimple constitution and a uniform processing over the workpiece can beachieved.

[0028] According to the ninth aspect of the present invention, since, inaddition to the constitution according to the seventh aspect of thepresent invention above mentioned, it has a constitution that theconstitution according to the seventh aspect can be achieved with asimple constitution and a uniform processing over the workpiece can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[0029]FIG. 1 is a schematic cross-sectional view of a plasma processingapparatus according to a first embodiment of the present invention;

[0030]FIG. 2 is another schematic cross-sectional view of the plasmaprocessing apparatus according to the first embodiment of the presentinvention;

[0031]FIG. 3 is the other schematic cross-sectional view of the plasmaprocessing apparatus according to the first embodiment of the presentinvention;

[0032]FIG. 4 is a schematic cross-sectional view of a plasma processingapparatus according to a second embodiment of the present invention;

[0033]FIG. 5 is a schematic plan view showing an example of theconstitution according to the second embodiment of the presentinvention.

[0034]FIG. 6 is a schematic cross-sectional view of a plasma processingapparatus wherein a connecting position of a pulse gas valve is changedin comparison to the second embodiment of the present invention;

[0035]FIG. 7 is a schematic plan view showing another example of theconstitution of a second embodiment of the present invention.

[0036]FIG. 8 is a schematic cross-sectional view of a plasma processingapparatus according to a third embodiment of the present invention;

[0037]FIG. 9 is a schematic cross-sectional view of a plasma processingapparatus according to a fourth embodiment of the present invention;

[0038]FIG. 10 is a schematic cross-sectional view of a plasma processingapparatus according to a fifth embodiment of the present invention;

[0039]FIG. 11 is a schematic enlarged plan view showing the partitionplate according to the fifth embodiment of the present invention;

[0040]FIG. 12 is a schematic cross-sectional view of a plasma processingapparatus according to a sixth embodiment of the present invention;

[0041]FIG. 13 is a schematic enlarged plan view showing the partitionplate according to the sixth embodiment of the present invention; and

[0042]FIG. 14 is a schematic cross-sectional view of a prior art plasmaprocessing device.

DETAILED DESCRIPTION OF THE INVENTION

[0043] Preferred embodiments of the plasma processing apparatusaccording to the present invention will be described below withreference to the accompanying drawings.

[0044] Embodiment 1

[0045]FIG. 1 is a schematic cross-sectional view of a plasma processingapparatus according to a first embodiment of the present invention. InFIG. 1, reference numeral 2 designates a processing chamber wherein aworkpiece, for example a wafer 8 is processed with plasma, referencenumeral 3 designates a plasma generating chamber wherein plasma isgenerated, and, in the present embodiment, reaction chamber 1 consistsof these two chambers 2 and 3. Reference numeral 4 designates apartition plate for partitioning the processing chamber 2 from theplasma generating chamber 3, reference numeral 5 designates holes whichare provided in the partition plate 4 and make the processing chamber 2in connection with the plasma generating chamber 3, reference numeral 6designates a exhaust port, reference numeral 7 designates a stage, andreference numeral 9 designates a pulse gas valve which is a gassupplying means to pulsatively supply the gases to the plasma generatingchamber 3. Reference numeral 10 designates a drive means for the pulsegas valve 9, reference numeral 11 designates a gas introducing line,reference numeral 15 designates a radio frequency antenna, referencenumeral 16 designates a radio frequency power supply, and referencenumeral 17 designates a quartz window.

[0046] In the present embodiment, the reaction chamber 1 is shaped in acylindrical form having, for example, a diameter of 40 to 50 cm and aheight of 20 to 30 cm. The stage 7 is shaped in a columnar form or adisc form and is arranged coaxially with the reaction chamber 1. In thepresent embodiment, the shapes of the reaction chamber I and the stage 7are not limited to cylindrical form, columnar form or disc form, howeverit is preferable that their shapes are axially symmetrical for uniformprocessing.

[0047] Further, in the present embodiment, the pulse gas valve 9 isarranged coaxially with the central axis of the reaction chamber 1 andthe exhaust port 6 in an annular or ring shape is also arrangedcoaxially with the central axis of the reaction chamber 1. In thepresent embodiment, the exhaust port 6 may not be in a contiguous ringshape, but may consists of a plurality of small ports, wherein eachsmall port is arranged concentrically around the central axis of thereaction chamber 1.

[0048] In the plasma processing apparatus having the constitution asdescribed above, the drive means 10 actuates the pulse gas valve 9 andthen the processing gas is pulsatively introduced into the plasmagenerating chamber 3. When a radio frequency voltage is applied to theradio frequency antenna 15 by the radio frequency power supply 16, anelectromagnetic field is formed within the plasma generating chamber 3through the quartz window 17. Then, inductively coupled plasma (ICP) isgenerated within the plasma generating chamber 3. The generated plasmaand neutral radicals are transported to the processing chamber 2 throughthe holes 5 in the partition plate 4. Then, the plasma and the neutralradicals become incident on (or strike) the surface of wafer 8 as asupersonic free jet caused by the pressure difference between the plasmagenerating chamber 3 and the processing chamber 2 and the intendedprocessing are achieved. And then, the neutral radicals and the reactionproducts produced by the wafer processing are exhausted through theexhaust ports 6.

[0049] The plasma processing apparatus according to the presentinvention is characterized in that one or more processing gases aresupplied by using the pulse gas valve 9, and plasma and neutral radicalsare jetted into the processing chamber 2 as a supersonic free jet makinguse of the pressure difference between the plasma generating chamber 3and the processing chamber 2.

[0050] In general, a gas flow becomes a supersonic free jet under thecondition as shown in Formula (1) as follows: $\begin{matrix}{\frac{P_{1}}{P_{2}} > \left( \frac{\gamma + 1}{2} \right)^{\gamma/{({\gamma - 1})}}} & (1)\end{matrix}$

[0051] The Mach disk of the supersonic free jet resides in the positionshown as follows: $\begin{matrix}{\frac{x_{d}}{d} = {0.67\sqrt{\frac{P_{1}}{P_{2}}}}} & (2)\end{matrix}$

[0052] In the above formulae (1) and (2), P₁ represents a pressure of agas storage container, P₂ represents a pressure of a container fromwhich the gases are jetted out, γ represents a ratio of specific heat ofthe gases, X_(M) represents a position of the Mach disk of thesupersonic free jet, and d represents a diameter of the nozzle. Sincethe hole of the nozzle is circular, the supersonic free jet is anaxially symmetrical flow. In the present embodiment, P₁ represents apressure of the plasma generating chamber 3 and P₂ represents a pressureof the processing chamber 2.

[0053] According to formula (2), at the instant when the processinggases are supplied through the pulse gas valve 9, the Mach disk of thesupersonic free jet (X_(M)) reaches a point which is thousands times ofthe nozzle diameter distant. Therefore, neutral radicals almostinstantly reach the surface of the workpiece 9. However, when the pulsegas valve 9 is closed, the pressure difference decreases and the valueof XM decreases. And when the pressure difference comes to not satisfythe condition of the formula (1), the gas flow becomes to a generalflow.

[0054] In the present embodiment, since a constitution that the pulsegas valve 9 is arranged coaxially with the central axis of the reactionchamber 1 and the exhaust port 6 is also arranged axially symmetricalwith respect to the central axis of the reaction chamber 1 is employed,even if a supersonic free jet is not formed, the gas flow and pressurefrom the pulse gas valve 9 to exhaust port 6 may be unified, so that auniform processing over the wafer 8 may be achieved.

[0055] In the embodiment shown in FIG. 1, the gas supplying direction bythe pulse gas valve 9 was arranged to correspond with the exhaustingdirection by said exhausting means. However, the arrangement is notnecessarily limited as above, but may be changed such a manner that thegases are axially introduced into the reaction chamber 1 from the topportion thereof and the exhausting direction is directed to a directionperpendicular to the axis of the reaction chamber 1 as shown in FIG. 2.Alternatively, the other arrangements may be employed, one of which isthat the gases are introduced in the direction perpendicular to the axisof the reaction chamber 1 from the sidewall and the exhausting directionis arranged to correspond with the axis of the reaction chamber 1 asshown in FIG. 3, and another is that the gases are introduced in thedirection perpendicular to the axis of the reaction chamber 1 and theexhausting direction is also directed to the direction perpendicular tothe axis of the reaction chamber 1, not shown in the drawings. In FIG.3, reference numerals 91 and 92 designate the pulse gas valvesrespectively, and reference numerals 111 and 112 designate the gasintroducing conduits respectively. In the embodiment of FIG. 3, twopulse gas valves 91 and 92 are arranged in the reaction chamber 1 sothat the two valves are axially symmetrical with respect to the centralaxis of the reaction chamber 1. In addition, the both drive means forthe pulse gas valves 91 and 92 are not shown in FIG. 3.

[0056] The present embodiment is described as to the apparatus havingthe partition plate 4, however, the same explanation is applicable tothe arrangement that does not have the partition plate 4 and both plasmageneration and plasma processing are performed in the same reactionchamber 1.

[0057] Embodiment 2

[0058] Then, a next embodiment will be explained, wherein the pulse gasvalve 9 and the exhaust port 6 are not coaxially arranged with thecentral axis of the reaction chamber 1 or they are not arranged in aposition axially symmetrical with respect to the central axis of thereaction chamber 1.

[0059]FIGS. 4 and 5 are schematic cross-sectional views of a plasmaprocessing apparatus according to a second embodiment of the presentinvention, wherein FIG. 4 is a schematic cross-sectional view and FIG. 5is a plan view. FIG. 6 is a schematic cross-sectional view of a plasmaprocessing apparatus wherein a connecting position of a pulse gas valveis changed in comparison to the second embodiment of the presentinvention. In the present embodiment, the pulse gas valve 9 and theexhausting port 6 are provided in the sidewall of the reaction chamber1, and the gas supplying direction by the pulse gas valve 9 is arrangedto correspond with the exhausting direction by said exhausting port 6.Further, as shown in FIG. 5, when observed from the directionperpendicular to the face to be processed of the wafer 8, the gassupplying direction by the pulse gas valve 9 is arranged to direct thecenter of the reaction chamber 1 and the arrangement and the exhaustingdirection of the exhausting port 6 is arranged to correspond with thegas supplying direction. To the contrary, in the comparative embodimentas shown in FIG. 6, the gas supplying direction by the pulse gas valve 9is arranged opposite to the exhausting direction by the exhausting port6.

[0060] Now, examples of etching process of substrates performed at thefollowing condition, using the apparatuses according to the presentinvention shown in FIGS. 4 and 5 and that of in the comparativeembodiment shown in FIG. 6 is described. In such processing, a substrateof a silicon substrate with an oxide film, and a substrate consisting ofthe above substrate, onto which a polycrystalline silicon is furtherdeposited are used. Etching condition: Opening time of the pulse gasvalve: 20 msec., Closing time of the pulse gas valve: 280 msec., meanflow rate of chlorine gas: 150 sccm, mean pressure in the processingchamber: 3 mTorr, Applied power to RF frequency antenna: 1800 W, AppliedRF bias power to substrate: 30 W.

[0061] As to the substrate on which polycrystalline silicon isdeposited, the uniformity of the etch rate was ±7% when the apparatusconstitution according to the present embodiment was used. To thecontrary, it was ±18% when the apparatus constitution according to thecomparative embodiment was used. As to the substrate on which only oxidefilm is deposited, the uniformity of the etch rate was ±5% in both caseswhen the apparatus constitution according to the present embodiment wasused and when the apparatus constitution according to the comparativeembodiment was used. According to this result, although the gas flow andthe pressure distribution scarcely exert an influence upon the etchingof the material such as oxide film where ion bombardment etchingreaction is dominant in the etching mechanism thereof, they exert nolittle influence upon the etching of the material such aspolycrystalline silicone where neutral radical species exert muchinfluence upon the etching processing. Therefore, in such processing, itis found that the apparatus according to the present embodiment achievesmore uniform processing. Further, in the above test, the uniformity ofthe etch rate was determined as follows:

[0062] The difference of the film thickness before and after etchingprocessing was measured at one point and divided by the processing timeto obtain the processing rate;

[0063] Such a measurement is made at 49 points; and

[0064] Statistical variation thereof is calculated.

[0065] Using the apparatus constitution where the pulse gas valve 9 isarranged on the sidewall of the plasma generating chamber 3, when aswitching operation (opening and closing operation) of the pulse gasvalve 9 is performed, the gases diffuse throughout the plasma generatingchamber 3 as a supersonic free jet according to the above formula (2) atthe instant when the pulse gas valve 9 is opened. However, when thepulse gas valve 9 is closed and the condition shown in the above formula(1) is not satisfied, the gas flow comes to a usual free molecular flowor Knudsen flow. Then the pressure distribution within the plasmagenerating chamber 3 becomes uneven, as a result, the pressuredistribution within the processing chamber 2 becomes uneven.Accordingly, the distribution of neutral radicals and reaction productcomes to uneven within the processing chamber 2, so that etchingprocessing comes to not uniform. Although in the case that anarrangement where the pulse gas valve 9 and the exhausting port 6 arecoaxially arranged with the central axis of the reaction chamber 1 as inthe embodiment 1 is not employed, even if a supersonic free jet is notformed, the deviation or unevenness of pressure and gas flow may bedecreased by employing an arrangement where the gas supplying directionby the pulse gas valve 9 is arranged to correspond with the exhaustingdirection by said exhausting port 6, and further, as shown in FIG. 5,when observed from the direction perpendicular to the face to beprocessed of the wafer 8, the gas supplying direction by the pulse gasvalve 9 is arranged to direct the center of the reaction chamber 1, andthe arrangement and the exhausting direction of the exhausting port 6 isarranged to correspond with the gas supplying direction as the presentembodiment.

[0066] Although the embodiment where the gas supplying direction by thepulse gas valve 9 is arranged to direct the center of the reactionchamber 1 and the arrangement and the exhausting direction of theexhausting port 6 is arranged to correspond with the gas supplyingdirection is shown in FIG. 5, almost the same effect may be obtainedwhen the exhausting ports are arranged in the reaction chamber 1 so thata line extending from the center of the reaction chamber 1 to theexhausting ports is oriented at an angle from −45 degree to +45 degreerelative to a line from the gas supplying means to the center of thereaction chamber 1 and the exhausting direction by the exhausting meansfrom the center of the reaction chamber 1 is also oriented at the sameangle as above when observed from the direction perpendicular to theface to be processed of the wafer as shown in FIG. 7.

[0067] The present embodiment is described as to the apparatus havingthe partition plate 4, however, the same explanation is applicable tothe arrangement that does not have the partition plate 4 and both plasmageneration and plasma processing are performed in the same reactionchamber 1.

[0068] Embodiment 3

[0069]FIG. 8 is a schematic cross-sectional view of a plasma processingapparatus according to a third embodiment of the present invention. InFIG. 8, reference numeral 93 designates a pulse gas valve and referencenumeral 113 designates a gas introducing line. In addition, each drivemeans for each pulse gas valve 91, 92 and 93 is not shown in FIG. 8. Inthe present embodiment, one pulse gas valve 91 is connected to theproximity of the exhaust means 6 and two pulse gas valves 92 and 93 areconnected to the opposite side of the exhaust means 6.

[0070] According to the above constitution, since the gas flow rates areincreased in the region apart from the exhaust means 6 due to the pulsegas valves 92 and 93, the deviation or unevenness of pressure and gasflow within the reaction chamber 1 may be prevented due to attaining abalance with the exhaust. Therefore, even if a supersonic free jet isnot formed, a uniform processing over the wafer can be achieved. Inaddition, since a plurality of pulse gas valves 91, 92 and 93 areconnected, such a constitution is useful for the case wherein aplurality kinds of gases are used.

[0071] In the present embodiment, the number of the pulse gas valves tobe connected to the reaction chamber 1 is not limited to three. Theimportant feature of the present embodiment is that a relatively smallnumber of the pulse gas valves is arranged in the proximity of theexhaust port 6 and the number thereof is increased as the distance fromthe exhaust port 6 increases. Therefore, almost the same effect isobtained by employing a constitution that the amount of the gasessupplied by the gas supplying means is set relatively small in theproximity of the exhaust ports 6 and the amount of the gases supplied bythe gas supplying ports 6 is increased at a position where its distancefrom the exhaust means increases.

[0072] In FIG. 8, an embodiment wherein the apparatus has no partitionplate, however, the same effect may be obtained when an apparatus havingthe partition plate.

Embodiment 4

[0073]FIG. 9 is a schematic cross-sectional view of a plasma processingapparatus according to a fourth embodiment of the present invention. InFIG. 9, reference numeral 94 designates a pulse gas valve and referencenumeral 114 designates a gas introducing line. In addition, each drivemeans for each pulse gas valve 91, 92, 93 and 94 is not shown in FIG. 9.In the present embodiment, each of a plurality of pulse gas valves maybe arranged to be connected to the sidewall of the reaction chamber 1 atoptional position, respectively. For example, two valves are arranged inthe proximity of the exhaust port 6 and the other two valves arearranged at the opposite side of the exhaust port 6. Then, the gas flowrates in the pulse gas valves 93 and 94 which are positioned apart fromthe exhaust port 6 are relatively increased and that in the valves 91and 92 which are positioned in the proximity of the exhaust port 6 arerelatively decreased. Thus, a constitution can be achieved, wherein theamount of the gases supplied by the pulse gas valve is made relativelysmall in the proximity of the exhaust port 6 and the amount is increasedas the distance from the exhaust port 6 increases. Accordingly, even ifa supersonic free jet is not formed, a uniform processing over the wafermay be achieved, preventing deviation or unevenness of pressure and gasflow within the reaction chamber 1. In addition, as in the case of thethird embodiment, it is useful for the case wherein a plurality kinds ofgases are used.

[0074] In FIG. 9, an embodiment wherein the apparatus has no partitionplate, however, the same effect may be obtained when an apparatus havingthe partition plate.

[0075] Embodiment 5

[0076]FIG. 10 is a schematic cross-sectional view of a plasma processingapparatus according to a fifth embodiment of the present invention andFIG. 11 is a schematic enlarged plan view showing the partition plateshown in FIG. 10. In the present embodiment, a number of the holes 5 isset at a relatively small figure in the proximity of the exhaust port 6and the number of the holes 5 is increased at a position where itsdistance from the exhaust port 6 increases. Accordingly, an openingratio of the holes 5, which means numbers of holes per unit area, is setsmall in the proximity of the exhaust port 6 and is set to increase asthe distance from the exhaust port 6 increases. Therefore, even if asupersonic free jet is not formed, it is possible to achieve a uniformtransferring rate or speed of the plasma gas from the plasma generatingchamber 3 to the processing chamber 2, so that deviation or unevennessof pressure and gas flow within the reaction chamber 1 can be prevented.Accordingly, a uniform processing over the wafer 8 can be achieved.

[0077] Embodiment 6

[0078]FIG. 12 is a schematic cross-sectional view of a plasma processingapparatus according to a sixth embodiment of the present invention andFIG. 13 is a schematic enlarged plan view showing the partition plateshown in FIG. 12. In the present embodiment, a diameter of a hole 5 isset at a relatively small figure in the proximity of the exhaust port 6and a diameter of the hole 5 is relatively increased at a portion whereits distance from the exhaust port 6 relatively increases. Accordingly,the opening ratio of the holes 5 is set small in the proximity of theexhaust port 6 and is set to increase at a portion where its distancefrom the exhaust port increases. Therefore, even if a supersonic freejet is not formed, it is possible to achieve a uniform transferring rateor speed of the plasma gas from the plasma generating chamber 3 to theprocessing chamber 2, so that deviation or unevenness of pressure andgas flow within the reaction chamber 1 may be prevented. Accordingly, auniform processing over the wafer 8 may be achieved.

[0079] In the above fifth and sixth embodiments, a straightening vanefor exhaustion may be arranged around the stage 7.

[0080] It should be understood by those skilled in the art that thearrangements and figures described in the above embodiments are notlimited to the specific details and representative embodiments butpresented for explanation only, and various modifications thereof arecontemplated as necessary within the scope of the invention.

What is claimed is:
 1. A plasma processing apparatus comprising areaction chamber for processing a workpiece with plasma which isgenerated by using one or more gases, a gas supplying means whichpulsatively supplies the gases to the reaction chamber, and an exhaustmeans for exhausting the reaction chamber, wherein a gas supplyingdirection by said gas supplying means is arranged to correspond with anexhausting direction by said exhausting means.
 2. The plasma processingapparatus according to claim 1, wherein when observed from a directionperpendicular to a face of the workpiece to be processed, the gassupplying direction by said gas supplying means directs to a center ofthe reaction chamber, and the exhausting means are arranged in thereaction chamber so that an assumed straight line extending from thecenter of the reaction chamber to the exhausting means is oriented at anangle from −45 degree to +45 degree relative to a line from the gassupplying means to the center of the reaction chamber and the exhaustingdirection by the exhausting means from the center of the reactionchamber is also oriented at the same angle as above.
 3. A plasmaprocessing apparatus comprising a reaction chamber for processing aworkpiece with plasma which is generated by using one or more gases, agas supplying means which pulsatively supply the gases to the reactionchamber, and one or more exhaust means for exhausting the reactionchamber, wherein the shape of the reaction chamber is axiallysymmetrical with respect to an central axis of the reaction chamber, thegas supplying means are arranged on the central axis or at axiallysymmetrical positions with respect to the central axis of the reactionchamber, and the exhaust means are also arranged at axially symmetricalpositions with respect to the central axis of the reaction chamber.
 4. Aplasma processing apparatus comprising a reaction chamber for processinga workpiece with plasma which is generated by using one or more gases, agas supplying means which pulsatively supplies the gases to the reactionchamber, and an exhaust means for exhausting the reaction chamber,wherein the amount of the gases supplied by the gas supplying means isset relatively small in the proximity of the exhaust means and theamount of the gases supplied by the gas supplying means is increased ata position where its distance from the exhaust means increases.
 5. Theplasma processing apparatus according to claim 4, wherein a number ofthe gas supplying means is set relatively small in the proximity of theexhaust means and the number of the gas supplying means is increased ata position where its distance from the exhaust means increases.
 6. Theplasma processing apparatus according to claim 4, wherein the gas flowrate is set at a relatively small figure in the proximity of the exhaustmeans and the figure of the gas flow rate is increased at a positionwhere its distance from the exhaust means increases.
 7. The plasmaprocessing apparatus comprising a reaction chamber for processing aworkpiece with plasma which is generated by using one or more gases, agas supplying means which pulsatively supplies the gases to the reactionchamber, an exhaust means for exhausting the reaction chamber, apartition plate which partitions the plasma generating chamber whereinplasma is generated from the processing chamber wherein a workpiece isprocessed with the plasma, and holes which are provided in the partitionplate and make the processing chamber in connection with the plasmagenerating chamber, wherein at least one of the number and the size ofthe holes is changed depending on the distance thereof from theexhausting means, thereby an opening ratio of the holes being set at arelatively small figure in the proximity of the exhaust port and thefigure thereof being relatively increased at a position where itsdistance from the exhaust means relatively increases.
 8. The plasmaprocessing apparatus according to claim 7, wherein a number of the holesis set at a relatively small figure in the proximity of the exhaust portand the number of the holes is relatively increased at a position whereits distance from the exhaust means relatively increases.
 9. The plasmaprocessing apparatus according to claim 7, wherein a size of the hole isset at a relatively small figure in the proximity of the exhaust portand the size of the hole is relatively increased at a position where itsdistance from the exhaust means relatively increases.